The present invention relates to electric motor systems, and more specifically to a braking mechanism for an electric motor.
Electric motors are used in a variety of applications ranging from simple kitchen equipment to complex naval systems. Safety is an important concern with some electric motors, because of their rotational momentum and the materials, particularly rigid materials, of which their moving parts are made. This is especially so for high velocity motors used to drive fans. Some such motors drive fans having exposed blades in normally enclosed environments where serious injury could result if the fan blades are contacted in operation. In an existing approach to such concern, an interlock is provided that removes the power from the fan motor whenever the closed environment is opened. However, depending on the momentum of the motor, a significant delay can result in stopping the fan upon removal of power. Hence, by this approach the interlock is only partly effective in preventing a mishap. The system having the fan still poses a risk of injury if the fan is contacted too soon after the interlock is opened upon opening the closed environment.
Some other ways that this concern has been addressed include systems that apply mechanical braking to the motor. Such systems only operate when the motor is in service for normal operation. If the motor is removed for servicing, the mechanical braking is no longer present, and the safety concern is left unaddressed. In another approach, a voltage supply line is connected to the motor through an engageable connector, the motor stopping when the connector becomes disengaged. However, while the motor is stopped upon disengaging the connector, the voltage supply line to the connector continues to remain live. Thus, the stopped motor gives one an unreasonable sense of safety since the connector continues to maintain the live supply line at some elevated voltage operative to stop the motor.
Accordingly, in view of the existing approaches, it would be desirable to provide a circuit capable of rapidly braking an electric motor without the need to maintain a live voltage at a connector and which can be provided with the motor in a brakeable motor unit to maintain braking capability even when the motor is being serviced.